The present invention relates to a liquid jetting apparatus such as a recording head for an ink jet recording apparatus, an electrode member ejection head for an electrode forming apparatus, an organic substance jetting head for a bio-chip manufacturing apparatus, or the like, which records images and characters on a recording sheet by ejecting ink droplets from nozzle orifices.
FIG. 17 shows a related-art ink jet recording apparatus, which is one kind of the liquid jetting apparatus, comprising: a carriage 3, wherein an ink cartridge 1 is mounted on the upper face while a recording head 2 is attached to the lower face, and a cap 4 for covering the recording head 2.
The carriage 3 is connected by a timing belt 5 to a stepping motor 6, and reciprocates along a guide bar 7 in the widthwise direction of a recording sheet 8. A drive circuit 9, which is arranged in a case 10 fixed to a wall frame 11, is provided to control the ejection of ink from the recording head 2. A drive signal output by the drive circuit 9 and various other control signals are transmitted to the recording head 2 by a flexible flat cable 12′.
The recording head 2 is attached to the face of the carriage 3 that is directed to the recording sheet 8 (in this example, the lower face). While the carriage 3 is moving, ink stored in the ink cartridge 1 is supplied to the recording head 2 and is ejected as droplets onto the top face of the recording sheet 8 to print images and characters formed as matrixes of dots.
The cap 4 is arranged in a non-printing region within the range of movement of the carriage 3, and while printing is halted, covers the nozzle face of the recording head 2 to prevent, to the extent possible, ink from drying in the nozzle orifices. Further, the cap 4 is connected to a suction pump 13, and during a cleaning process, a negative pressure is applied to the recording head 2 to draw ink from the nozzle orifices. Furthermore, the cap 4 can also serve as a reservoir for ink droplets that are discharged from the recording head by a flushing operation.
While the carriage 3 is reciprocating and printing is being performed, drive signals transmitted by the drive circuit 9 are carried to the recording head 2 by the flexible flat cable 12′, which is repetitively bent. As is shown in FIG. 18, the flexible flat cable 12′, which is formed of a flexible and durable synthetic resin 15 that can withstand repeated bending, is shaped like a belt, and within it and constituting multiple conductive lines, conductive patterns 14 are arranged in parallel. In order for the same durability as that exhibited by the synthetic resin 15 to be provided for the conductive patterns 14, they are formed by cutting into narrow strips an extremely thin copper alloy plate.
There are about 30 conductive patterns 14, and in addition, for the several pressure generating elements that depend on a number of different ink types, a ground line, a temperature detection signal line and other power feed lines are provided. Currently, it is necessary for the number of ink types to be increased in order to improve the printing quality, or for the number of signal types transmitted by the drive circuit 9 to the recording head 2 to be increased so as to adapt a recording apparatus to the environmental conditions, such as the temperature and the humidity, in the location whereat it is installed.
As the easiest measure for coping with either of these needs, the width of the flexible flat cable 12′ and the number of conductive patterns 14 can be increased. However, when a wider flexible flat cable 12′ is continuously bent during printing, it can interfere with associated, peripheral members and prevent the printing operation from being performed smoothly. Otherwise, if the torsional deformation of a wide flexible flat cable 12′ occurs, its ends may be stretched too far and torn when it is bent during printing.
In order to resolve these problems, one measure has been proposed whereby, as is shown in FIG. 19, the flexible flat cable 12′ is divided into a first flexible flat cable 12′A and a second flexible flat cable 12′B, and these cables 12′A and 12′B are laminated.
FIG. 20A shows the polarities of the conductive patterns 14 of the first and second flexible flat cables 12A and 12B. The hatched conductive patterns 14 represent the positive polarity, and the non-hatched conductive patterns 14 represent the negative polarity.
In such a lamination structure, when the opposite polarities face each other and the two types of conductive patterns 14 are rendered conductive at the same time, the magnetic fields of both conductive patterns 14 are generated in reverse directions, as indicated by the arrows in FIGS. 20A and 20B. In FIG. 20B, only the polarities are depicted for better understanding.
Therefore, the amount of current supplied to the recording head 2 is reduced by a mutual inductance generated between the conductive patterns 14. Accordingly, insufficient drive energy tends to be supplied to the pressure generating elements of the recording head 2, and desired ink ejection can not be performed.
Specifically, an ink ejection shortage will affect only a specific nozzle orifice array of the recording head 2, but due to the pertinent nozzle orifice array, a printing failure will occur that renders all printing results abnormal.